The subject matter disclosed herein relates to couplings and, in particular, to electrical isolating rings in couplings.
Many applications require that rotating shafts be coupled together. For example, generators are driven by industrial turbines to produce electricity. A load coupling is often used to connect the shafts of the generator and the turbine. The coupling is typically electrically insulated to prevent current traveling down the rotor shafts. If current is transmitted to the rotor of the turbine, there is a possibility of electrical arcing from the rotor to the bearing surfaces, which can cause damage and potentially failure of the bearings.
In more detail, in one class of couplings for rotating shafts, a drive portion of the coupling is coupled to a driving shaft by a group of circumferentially spaced fasteners. A driven portion of such a coupling is similarly coupled to a driven shaft. The two parts of the coupling are then coupled together by connecting bolts. During rotation, the driving shaft applies a force that is transmitted through the connecting bolts to the driven shaft.
Typically, the drive portion is electrically isolated from the driven portion by a spacer ring disposed between the two. The prevailing approach to providing electrical isolation is through the use of a fiberglass reinforced epoxy (FG/Ep) insulating assembly. The insulating assembly typically includes four elements: an insulating plate, bushings, washers and a pilot ring.